1. Field of the Invention
The present invention is related to a process for making a dry-spun spandex and, more particularly, to the use of poly(N-vinyl-2-pyrrolidone) with elastomeric segmented polyurethanes for the dry-spinning process.
2. Description of Background Art
Because of its excellent stretch characteristics, spandex is extensively used in garments such as legwear, innerwear, and sportswear. Reliable fiber spinning is economically advantageous during manufacture of the fiber because waste is reduced.
Japanese Published Patent Application 48-80150 discloses the use of poly(N-vinyl-2-pyrrolidone) in making wet-spun polyurethane- and polyurethaneurea-based spandex to improve whiteness retention.
There is a need for a polyurethane which has very good dry-spinnability into spandex.
The process of this invention for preparing spandex comprises the steps of:
A. preparing a polymer solution of an elastomeric segmented polyurethane based on 1,1xe2x80x2-methylenebis(4-isocyanatobenzene), a polyether glycol selected from the group consisting of poly(tetramethyleneether)glycol and poly(tetramethyleneether-co-3-methyltetramethylene-ether) glycol, and a diol selected from the group consisting of ethylene glycol, 1,3-propane diol, and 1,4-butane diol;
B. adding to the solution prepared in step A 1-10% by weight of total polymer solids content a polymer selected from the group consisting of poly(N-vinyl-2-pyrrolidone) and PVP copolymers;
C. dry-spinning the solution prepared in step B to form spandex; and
D. winding up the spandex.